1. Field of the Invention
The present invention relates to a plate making device and method, and particularly to a plate making device and method for forming a perforation image on a stencil plate with heat-perforating means.
2. Description of Related Art
A stencil plate as disclosed in Japanese Unexamined Patent Publication No. 61-72590 has been hitherto known as an ink-containing stencil plate used for a stamp device for stencil printing. The stencil plate as described above will be described with reference to FIGS. 10A and 10B.
As shown in FIGS. 10A and 10B, the stencil plate 50 comprises a heat sensitive stencil paper 54 formed of a thermoplastic film 51 and a porous supporting member 53, non-woven cloth 56 serving as an ink-impregnated member, a frame 57 disposed so as to surround the non-woven cloth 56, and a film 58 serving as an ink-impermeable base member, all of which are successively laminated. Adhesive agents 59 are provided between the heat sensitive stencil paper 54 and the frame 57. Adhesive agents 52 are provided between the thermoplastic film 51 and the porous supporting member 53.
A perforation image is formed on the thus-constructed stencil plate 50 by heat-melting the thermoplastic film 51 of the heat sensitive stencil paper 54 with a stamp device using a thermal head, for example (see reference numeral 1 in FIG. 2) (formation of a perforation image is hereinafter referred to as "plate making"). The plate-made stencil plate 50 is installed into a stamp member 60 shown in FIG. 11(see FIG. 2), and stencil printing is performed by pushing the stamp member 60 against a print sheet 70. The stamp member 60 includes a grip 61, a cushion layer 62, and an adhesive layer 63.
Through experiment, it has been determined that the ink used for the stencil plate 50 as described above has characteristics as shown in FIG. 12. That is, in order to enable the printed ink to dry rapidly, the viscosity of the ink should be reduced. However, in this case, the ink is liable to be blurred, and thus, print quality is lowered. When the ink viscosity is low, ink flow is improved for a harder ink-impregnated member, and thus, the print quality is improved.
When the ink-impregnated member is hard, there is good contact between the thermal head and the stencil paper in a plate-making process for the stencil paper, and thus, heat energy of the thermal head is easily transferred to the stencil paper so that a perforation image is easily formed. In this case, if the stencil paper has high sensitivity to perforation, perforated holes would be large. Therefore, the perforation sensitivity of the stencil paper must be lowered or energy to be applied to the thermal head must be reduced.
Further, in order to improve the print quality without concern of ink dryness, that is, using ink having low dryness, the ink viscosity must be increased, the ink-impregnated member must be soft, the stencil paper sensitivity must be improved and the energy to be applied to the thermal head must be increased.
As described above, various characteristic combinations may be proposed among the stencil paper, the ink and the ink-impregnated member that are used for the stencil printing. However, when the energy to be applied to the thermal head is constant, there occur problems in that in some cases, sufficient perforation cannot be performed in accordance with the type of the stencil plate, and the perforated holes can be excessively large.